Separation membranes that separate a fluid or the like are classified into various types according to the differences in the pore size and separation function thereof. However, even in separation membranes different in type, they have a commonality in that when a raw fluid is supplied to one surface of the separation membrane, a permeate fluid separated from the raw fluid by permeating the separation membrane is obtained from the other surface. The separation membrane can be applied to a separation membrane element used for reverse osmosis-filtration. For example, the spiral separation membrane element includes a water collection tube with holes, and includes a channel material on the feed side wound around the water collection tube, a separation membrane and a channel material on the permeate side. The channel material on the feed side supplies the raw fluid to a feed fluid side of the separation membrane. The separation membrane separates components contained in the raw fluid. The channel material on the permeate side guides a permeate fluid which has permeated the separation membrane and separated from the raw fluid to a holed water collection tube. The spiral separation membrane element can take out a large amount of a permeate fluid by applying pressure to the raw fluid.
The resistance (i.e., pressure loss) generated when the raw fluid flows through a flow path on the feed side of the spiral separation membrane element is greatly dominated by a channel material on the feed side. Therefore, nets having various structures are reported for the purpose of reducing the pressure loss (for example, refer to Japanese Patent Laid-open Publication Nos. 2000-000437, 2000-042378 and 2005-305422).
On the other hand, in a spiral membrane separation apparatus described in Japanese Utility Model Laid-open Publication No. 59-44506, mesh-like members for a raw solution flow path corresponding to a channel material on the feed side are arranged at both ends of the membrane separation apparatus.
Japanese Patent Laid-open Publication No. 2004-50081 points out a problem that the member for a raw solution flow path described in JP '506 is not fixed to a separation membrane, and proposes the following spiral membrane element to solve this problem. That is, in the spiral membrane element described in JP '081, raw water spacers and are fixed to an end on a flow-in side of raw water of the separation membrane, or fixed to the end on the flow-in side of raw water and an end on a flow-out side of concentrate water. The raw water spacers are fixed to the ends of the separation membrane by being bonded with an adhesive or by being arranged such that a folded raw water spacer sandwiches the end of the separation membrane between the folded faces.
Conventional techniques are not sufficient in reducing the resistance of the raw fluid and the pressure loss, and there is room for improvement to increase the amount of water produced. Particularly, in the conventional techniques, the morphology of the channel material on the feed side is limited to a net, and the degree of freedom of change in the shape is low.
It could therefore be helpful to provide a technique which enables changing the shape of the channel material on the feed side according to the type of a raw fluid, or a permeate fluid or a concentrate fluid to be obtained by enhancing the degree of freedom of change in the shape of the channel material on the feed side.